Double piston rod

ABSTRACT

A distance measuring apparatus for detecting the position of a reflection body in a line structure is provided that includes a sensor device, which has at least one antenna for feeding a transmission signal as an electromagnetic wave into the line structure and for receiving the electromagnetic wave reflected on the reflection body. The sensor device also includes evaluation electronics which are configured to determine the position of the reflection body from the phase difference between the transmitted and the received wave.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority and thebenefit of the filing date of U.S. patent application Ser. No.12/673,754, which claims priority and the benefit of the filing date ofPCT Application No. PCT/EP2008/006778, filed Aug. 18, 2008 and GermanApplication No. DE 10 2007 038 718.2, filed Aug. 16, 2007, the subjectmatter of each of which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates generally to distancemeasuring devices.

In fixed-pipe process plants of the food and pharmaceutical industry,pneumatic valves are used as

(a) single-seated blocking valves for simple blocking at pipelineintersections;

(b) single-seated two-way valves for combining products from twopipelines in one pipeline and for dividing one pipeline into twopipelines; and

(c) double-seated valves for mix-proof separation of adverse products atpipeline intersections.

The precise function of the valves is described e.g. in the companybrochures of the companies GEA/Tuchenhagen and Alfa Laval.

In order to control the process it is necessary to detect the positionof the valves. For this purpose sensors such as potentiometers, LVDTs orjust simple reed switches are used. All of these sensors are complex tofit, are partially subject to mechanical wear and tear, and requireadditional external space.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with various embodiments, a distance measuring apparatusfor detecting the position of a reflection body in a line structure isprovided that includes a sensor device, which has at least one antennafor feeding a transmission signal as an electromagnetic wave into theline structure and for receiving the electromagnetic wave reflected onthe reflection body. The sensor device also includes evaluationelectronics which are configured to determine the position of thereflection body from the phase difference between the transmitted andthe received wave.

In accordance with other various embodiments, a pneumatic valve having adistance measuring apparatus for detecting the position of a reflectionbody in a line structure is provided that includes a sensor device,which has at least one antenna for feeding a transmission signal as anelectromagnetic wave into the line structure and for receiving theelectromagnetic wave reflected on the reflection body. The sensor devicealso includes evaluation electronics which are configured to determinethe position of the reflection body from the phase difference betweenthe transmitted and the received wave.

In accordance with yet other various embodiments, a method for detectingthe position of a reflection body within a line structure which isimplemented by a distance measuring apparatus is provided. The methodincludes feeding a transmission signal as an electromagnetic wave intothe line structure, receiving the electromagnetic wave reflected on areflection body, and determining the position of the reflection bodyfrom the phase difference between the transmitted and the received wave.

BRIEF DESCRIPTION OF THE DRAWINGS

The following exemplary embodiments of the invention are described ingreater detail by means of drawings. These show as follows:

FIG. 1 a sectional illustration of the mechanical structure of thedistance measuring apparatus according to various embodiments of theinvention in a single-seated valve;

FIGS. 2A and 2B diagrammatic illustrations of the structure of thedistance measuring apparatus according to various embodiments of theinvention in double-seated valves; and

FIGS. 3A and 3B sectional illustrations of the structure of the distancemeasuring apparatuses according to various embodiments of the inventionaccording to FIGS. 2A and 2B.

Parts corresponding to one another are provided with the same referencenumbers in all of the figures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the mechanical structure of the sensor (microwave sensor) 2for all applications with which just one piston 4 needs to be detected(single-seated valves, blocking valves, two-way valves). Here the pistonrod 6 passes within a so-called guide pipe 8. The guide pipe 8 isconnected securely to the end cover 10. At the end of the guide pipe 8there is an antenna 12 as described in German Application No. 102 05904.7. A coaxial wave is fed to the antenna (coupling probe) 12, forexample by means of a plastic insert 14, and via the probe 12 into ahollow conductor wave 15, for example in the E01 mode, radiated into theguide pipe 8, the injection of the electromagnetic wave 15 being amechanical step 16. The wave 15 is reflected on the piston rod 6 andreceived again by the antenna 12, is converted here once again into acoaxial wave, and by means of downstream signal processing the phasedifference between the transmitted and the received wave 15 is evaluatedin order to thus determine the position of the piston rod 6. At the endof the piston rod 6 an HF short circuit can in turn be provided in theform of two discs 17 with dielectric filler, for example with PPS40material. By appropriately selecting the field type of the wave, forexample E01, it is moreover possible to provide a hole 18 centrally inthe piston rod 8 in order, for example, to convey compressed air ontodownstream systems.

With double-seated valves 20 the position of two piston rods 6, 22passing into one another is to be detected simultaneously. FIGS. 2A, 2B,3A and 3B show the configuration. Here the inner piston rod 6 passeswithin a guide pipe 8, as already described for the single-seated valves5. The microwave sensor 2 and its injection via the antenna 12 are alsoidentical. In order to detect the second, outer piston rod 22 a coaxialsystem 24 is realized. Here the guide pipe 8 serves as an innerconductor 26 of the coaxial system 24 for the detection of the second,outer piston rod. The coaxial structure of the coaxial system 24 servesin turn as an inner conductor of the coaxial structure for the detectionof the next outermost piston rod, etc. The electromagnetic wave 28 isinjected by means of inductive coupling to this inner conductor 26. Forthis purpose a two- or more stage crossover 30 is realised in order toprovide HF adaptation. The inductive coupling comprises two or moreround discs 32, 34 the outer diameter of which becomes smaller andsmaller, and which are connected securely and with electricalconductivity to the guide pipe 8, for example by screwing.

Here the discs (rings) with a decreasing outer diameter serve aselectric transformation stages in order to achieve a reduced or minimumreflection factor with the injection of the electromagnetic wave intothe coaxial system. The inductive crossover 30, i.e. the disc 32 withthe largest diameter 36, is contacted directly on the outside 38 by thecoaxial feed line 40, 42. Since contacting must take placesymmetrically, at least 2 feed lines 40, 42 are used. There can ofcourse, however, also be 4, 8, 16 etc. contactings symmetricallydistributed over 360 degrees. The TEM mode or preferably the coaxial H11mode is produced as a wave type. FIGS. 2A and 2B show the wave progressfor both sensors 2, 24. Here too the coaxial feed line 40, 42 of theelectromagnetic wave 28 from the transmission/receiving module 44 isimplemented, for example, by means of pressure-tight glassification or aplastic insert 46.

The transmission and receiving and evaluation electronics 44 are locatedin the space behind the injection plate 48. The coaxial antenna feedline 12, 40, 42 through the injection plate 48 is connected directly tothe transmission/receiving electronics 44. The latter are generallyfitted on the conductor plate, e.g. in the form of SMD components.

The transmission frequencies range from a few hundred MHz to approx. 100GHz depending on the mechanical design of the drives. Moreover, over awide range of well-established valve sizes, the diameter of the pistonrods 6, 22 and of the guide pipe 8 can remain constant, and so thesensor 2, 24 can be used universally.

Thus, various embodiments provide a distance measuring apparatus fordetecting the position of a reflection body in a line structure which isparticular easy to fit, does not require any additional external space,and is not subject to mechanical wear and tear during operation. Othervarious embodiments provide a method for detecting the position of thereflection body within the line structure as well as a pneumatic valvewith this type of distance measuring apparatus.

A sensor device and the evaluation electronics formed in accordance withvarious embodiments can be totally integrated into the valve, and infact into the line structure or into an electronics space positionedfacing away from the line structure and behind the antenna injecting theelectromagnetic wave. Furthermore, it is advantageous that the distancemeasuring apparatus functions without any contact. Moreover, with thedistance measuring apparatus and the method according to the variousembodiments, the position of the reflection body within the linestructure can be established with great precision.

When using the distance measuring apparatus in a valve, in particularwith a pneumatic valve, the cylinder of the latter, in which a piston isoperated moveably, advantageously serves as a line structure.

In contrast to the prior art, various embodiments of the microwavesensor (sensor device) can be integrated fully into the piston space ofthe cylinder of the pneumatic valve, and measures the position of thevalve without any contact and with great precision.

In order to detect the piston moveable within the cylinder, the faceside of the piston rod of the piston acts as a reflection body.

In order to reflect the electromagnetic wave, the face side of thepiston rod is advantageously in the form of a short circuit for theelectromagnetic wave. Suitable as a short circuit for theelectromagnetic wave is a structure in the form of two or more metallicdiscs with dielectric filler, it being possible to fit the structure onthe face surface of the piston rod.

Further, two or more piston rods passing into one another can bedetected simultaneously and independently of one another so that thedistance measuring apparatus can also be used, for example, with doubleseated valves.

In order to feed the transmission signal into the line structure witheconomy of space, frequency precision and no contact, injection of theelectromagnetic wave in order to detect the innermost piston rod isadvantageously implemented capacitively or by means of a coupling slot.

In order to obtain the smallest possible reflection factor wheninjecting the electromagnetic wave it is advantageous to implement intothe line structure by means of an electric transformation stage. Theelectric transformation stage may be implemented as a mechanical stepwhich is advantageously provided with a decreasing step height in thedirection of the reflection body close to the window within the linestructure.

In order to achieve movement of the electromagnetic wave within the linestructure, to detect the innermost piston rod, and to obtain a veryaccurate result when determining the position, the frequency range ofthe electromagnetic wave advantageously comes between a few MHz and 100GHz.

In order to detect the innermost piston rod, the electromagnetic wave isadvantageously injected in the E01 mode.

In order to detect a second, outer piston rod on the double-seatedvalve, it is advantageous for the sensor device to comprise a coaxialsystem.

In order to realize the coaxial system for the detection of a second,outer piston rod, for example on the double-seated valve, a guide pipe,wherein the inner, first piston rod is operated, advantageously acts asan inner conductor of the coaxial system.

In order to detect further piston rods adjoining to the outside, thecoaxial structure of the second, outer piston rod advantageously servesas an inner conductor of the coaxial structure, etc.

In order to detect the second, outer piston rod, the electromagneticwave is advantageously injected inductively into the coaxial system. Forthis purpose metallic rings, which are advantageously connected securelyand with electrical conductivity to the guide pipe which serves as aninner conductor of the coaxial system, and the outer diameter of whichdecreases in the direction of the piston rod, are advantageous.

For the electrically conductive connection of the metallic rings and theguide pipe with the coaxial feed pipe connected to the latter, aninductive crossover from the ring with the largest diameter to thecoaxial feed pipe is provided. Advantageously, the inductive crossoverbetween the coaxial feed line and the ring with the largest diameter isimplemented symmetrically, and at least twice offset by 180° or fourtimes offset respectively by 90° between the individual contactings oreight times offset respectively by 45° between the individualcontactings on the ring.

The detection of the second, outer piston rod and further, outer pistonrods by means of the electromagnetic wave with frequencies within thefrequency range of a few MHz to 100 GHz takes place dependently upon thediameter of the piston rod within the coaxial system.

In order to detect the outer piston rods the electromagnetic wave isadvantageously injected in the TEM or over-moded H11 mode.

In order to convey compressed air onto downstream systems, the pistonrod may have one or more holes when injecting the electromagnetic wavein the E01 mode. Advantageously the hole/s is/are provided centrally inthe piston rod.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the variousembodiments of the invention without departing from their scope. Whilethe dimensions and types of materials described herein are intended todefine the parameters of the various embodiments of the invention, theembodiments are by no means limiting and are exemplary embodiments. Manyother embodiments will be apparent to those of skill in the art uponreviewing the above description. The scope of the various embodiments ofthe invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Moreover, in the following claims, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to impose numerical requirements on their objects.Further, the limitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

This written description uses examples to disclose the variousembodiments of the invention, including the best mode, and also toenable any person skilled in the art to practice the various embodimentsof the invention, including making and using any devices or systems andperforming any incorporated methods. The patentable scope of the variousembodiments of the invention is defined by the claims, and may includeother examples that occur to those skilled in the art. Such otherexamples are intended to be within the scope of the claims if theexamples have structural elements that do not differ from the literallanguage of the claims, or if the examples include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

The invention claimed is:
 1. A cylinder having a distance measuringapparatus, comprising: a cylinder casing; a coaxial system includingfirst and second coaxial piston rods, the first piston rod being locatedinside the second piston rod, the first piston rod having a firstreflective surface, the second piston rod having a second reflectivesurface; at least one antenna for feeding transmitted electromagneticwaves into the cylinder and for receiving electromagnetic wavesreflected off of the first and second reflective surfaces, at least oneof the antennas being a capacitive means or a coupling slot; evaluationelectronics coupled to the at least one antenna and being configured todetermine the position of the reflective surfaces from the phasedifferences between the transmitted waves and the waves reflected off ofthe first and second reflective surfaces; and a short circuit for theelectromagnetic wave located on the first or second reflective surface,the short circuit comprising two or more metallic discs having adielectric finer there between.
 2. The cylinder according to claim 1,wherein the cylinder has a first guide pipe for transmitting theelectronic wave to the first reflective surface and a second guide pipefor transmitting the electronic wave to the second reflecting surface,at least one of the antennas comprising an electric transformationstage.
 3. The cylinder according to claim 2, wherein the electrictransformation stage is a mechanical step.
 4. The cylinder according toclaim 1, wherever the electromagnetic wave is fed into the cylinder witha frequency range of about a few MHz to about 100 GHz based on thediameter of the first piston rod in a round hollow conductor mode, inthe EOI mode.
 5. The cylinder according to claim 1, wherein theelectromagnetic wave is injected into the coaxial system inductivelywith metallic rings having different outer diameters.
 6. The cylinderaccording to claim 5, wherein the contacting of one of the rings withthe largest outer diameter is symmetric, and at least twice offset by180 degrees or four times offset, respectively, by 90 degrees betweenthe individual contactings or eight times offset, respectively, by 45degrees between the individual contactings.
 7. The cylinder according toclaim 1, wherein the electromagnetic wave is fed into the coaxial systemin one of a TEM or over-moded H11 mode, with a frequency range of abouta few MHz to about 100 GHz based on the diameter of the second pistonrod for the detection of the position of the second piston rod.
 8. Thecylinder according to claim 1, wherein the first piston rod includes oneor more holes in order to convey compressed air for controllingdownstream systems.
 9. A cylinder having a distance measuring apparatus,comprising: a cylinder casing; a piston rod having a reflective surface;at least one antenna for feeding transmitted electromagnetic waves intothe cylinder and for receiving electromagnetic waves reflected off ofthe reflective surface; evaluation electronics coupled to the at leastone antenna and being configured to determine the position of thereflective surface from the phase differences between the transmittedwaves and the waves reflected off of the reflective surface; and a shortcircuit for the electromagnetic wave located on the reflective surface,the short circuit comprising two or more metallic discs having adielectric filler there between.